1. Field of the Invention
The present disclosure relates to focus detection apparatuses.
2. Description of the Related Art
Autofocus cameras that change the focus of an imaging lens and automatically bring the imaging lens into focus are in widespread use. Some cameras are provided with a focus detection apparatus that uses pixel signals from a sensor-array block arranged with respect to a focus detection area to detect a phase difference between two images. If the pixel signals from the sensor-array block are low, the signal-to-noise ratio is reduced and thus focus detection cannot be performed with high accuracy. Accordingly, a comparator is used to determine whether or not a pixel signal that increases with charge accumulation exceeds a threshold (hereinafter, this determination is referred to as termination determination), and if it is determined that the pixel signal exceeds the threshold, the charge accumulation is terminated, and focus detection is performed using the pixel signal at that time. There are some phase difference detection type focus detection apparatuses in which sensor-array blocks are arranged with respect to a plurality of focus detection areas, and focus detection can be performed in the respective focus detection areas. Japanese Patent Laid-Open No. 11-150686 proposes a focus detection apparatus that includes a plurality of sensor-array blocks and in which one comparator for use for the termination determination is shared with the plurality of sensor-array blocks, leading to a reduction in the chip area.